Railway track circuit apparatus



Sept. 24, 1935. H G, w T 2,015,577

' RAILWAY TRACK CIRCUIT APPARATUS Filed Nov. 9, 1954 I 4 6 la 9; 8 Z0 5 T Q /T2 1 I2 19 22 [6 7 I I8 TH" FLg. Z. ,l

122 7 TB I A Fig. 2.

INVENTOR H16 ATTORNEY Patented Sept. 24, 1935 UNETE STATES PATENT OFFICE RAILWAY TRACK CIRCUIT APPARATUS Application November 9, 1934, Serial No. 752,291

14 Claims.

My invention relates to railway track circuit apparatus, and has for an object the provision of novel and improved apparatus for expediting the release of the track relay armature when a ve- 5 hicle enters the section with which the track relay is associated. Apparatus embodying my invention also provides an improved shunting sensitivity for the track circuit. Other features and advantages of my invention will appear as the 10 specification progresses.

I will describe two forms of apparatus embodying my invention, and will then point out the novel features thereof in claims.

The present application is a continuation of 15 my copending application, filed August 23, 1933,

Serial No. 686,425, for Railway track circuit apparatus, in so far as the subject matter common to the two cases is concerned.

In the accompanying drawing, Fig. 1 is a dia- 20 grammatic view showing one form of track circuit apparatus embodying my invention. Fig. 2 is a diagrammatic view showing a modified form of relay combination also embodying my invention.

25 In each of the Views like reference characters designate similar parts.

Referring to Fig. 1, the reference characters I and Ia designate the traffic rails of a stretch of railway track which are formed by insulated rail 30 joints 2 into a track section A--B. The track section A-B is provided with a track circuit which comprises as its essential elements the trailic rails bonded in the customary manner, a source of periodic current connected across the 35- rails at one end of the section and a track relay adapted to receive energy from the trafiic rails at the other end of the section. In Fig. 1, the secondary winding 3 of a track transformer T has one terminal connected with the rail Ia by a wire 4 and its opposite terminal connected with the rail I by a wire 5, a current-limiting resistor 6 being interposed in the wire 5. The primary winding l of the track transformer T is connected with any convenient source of periodic 45 current such as an alternating current generator not shown in the drawing. It follows that the transformer T constitutes a source which continuously supplies alternating current to the trafiic rails of the section A-B.

50 At the opposite end of the section AB, a

transformer T2 has its primary winding 8 connected with the rails I and la by wires 9 and II), respectively, and hence the alternating current supplied to the trafiic rails at the left-hand end 55 of the section induces a corresponding alternating current in the secondary winding I I of the transformer T2. Conductors I4 and I connect the secondary winding H of transformer T2 with the input terminals I2 and I3, respectively, of a voltage doubler network designated as a whole by 5 the reference character VD. The voltage doubler network VD includes two rectifying units RI and R2 and two electrical condensers CI and C2 connected to form a bridge circuit network, the arrangement being such that the rectifying units 10 RI and R2 and the condensers CI and C2 are each included in a respective arm of the bridge as will be readily understood by an inspection of the drawing.

A track relay TR. is connected with the output terminals I 6 and I1 of the voltage doubler network VD by wires IB and I9, respectively. The relay TR is preferably a direct current neutral relay of a type commonly employed with track circuit apparatus. The relay TR is provided with an armature 20 which may be utilized for controlling traffic governing devices in any desired manner.

The voltage doubler circuit network VD functions in the following manner: During the half cycle of the alternating current that the lefthand terminal of the secondary winding II is positive, current will flow over wire I4, input terminal I2, rectifying unit RI in its low resistance direction, terminal I! and into the condenser CI and condenser CI will take a sufficient charge to bring its plates to a diiference of potential substantially equal to the maximum value of the electromotive force induced in the secondary winding II, the plate towards the ter-' minal I! being the positive plate and the plate towards the terminal I3 being the negative plate. During this half cycle'of the alternating current, current will also pass to the terminal I! and thence through the winding of the relay TR, by 40 a circuit to be shortly described.

On the next half cycle of the alternating current, the right-hand terminal of the secondary winding II will be positive and current will flow over wire I5, input terminal I3, condenser C2, terminal I6, rectifying unit R2 in its low resistance direction, terminal I2 and wire I4 to the lefthand terminal of the secondary winding II; and condenser 02 will take a suificient charge to bring its plates to a difference of potential substantially equal to the maximum value of the electromotive force induced in the secondary winding II, the plate towards the terminal I3 being the positive plate and the plate towards the terminal I ;6 being the negative plate. During this last mentioned half cycle of the alternating current, current will pass from the positive plate of the condenser CI, which condenser was charged during the previous half cycle of the alternating current as described above, over terminal II, wire I9, winding of the track relay TR, wire l8, terminal I6, rectifying unit R2, terminal I2, wire I4, secondary winding I I, wire I5, terminal I3 and to the negative plate of the condenser CI, and relay TR will be energized. That is to say, the condenser CI and the secondary winding II form two sources of electrical energy which function serially during this half cycle to supply current to the winding of the relay TR. The electromotive force of the condenser CI and that of the secondary winding II being additive in the circuit, the result will be that the electromotive force applied to the winding of the relay TR will be substantially double that induced in the secondary winding II. Furthermore, this circuit including the secondary winding II, condenser CI, winding of the relay TR and rectifying unit R2 is a circuit comprising inductance, capacity and resistance, the parts of which are preferably so proportioned and adjusted that the circuit is tuned to resonance at the frequency of the alternating current supplied by the track transformer T with the result that the current will have a maximum value. To make the tuning effect more prominent, transformer T2 may be so designed as normally to operate on the non-linear portion of the saturation curve whereby a change in the current flowing in winding 8 will vary the inductance to detune the circuit which supplies current to relay TR.

On the next half cycle of the alternating current, the left-hand terminal of the secondary winding I I is again positive and current will flow through the rectifier RI to the terminal I1 and thence into the condenser Ci, which was discharged during the previous half cycle of the alternating current, to again charge this condenser in the manner described hereinbefore. During this half cycle of the alternating current, energy will pass from the positive plate of the condenser C2, which was charged during the previous half cycle, to the terminal I3 and thence over wire I5, secondary winding I I of transformer T2, wire I4, terminal I2, rectifying unit RI, terminal Il, wire I9, winding of relay TR, wire I8, terminal I6 and to the negative plate of the condenser C2, and relay TR will be energized. That is to say, the condenser C2 and the secondary winding II now form two sources of electrical energy which function serially to supply current to the winding of the relay TR. The electromotive force of the condenser C2 and that of the secondary winding II being additive in the circuit, the result will be that the electromotive force applied across the winding of the relay TR will be substantially double that induced in the secondary winding II. Furthermore, the circuit including the secondary winding II, condenser C2, winding of relay TR and the rectifying unit RI is a circuit comprising inductance, capacity and resistance, the parts of which are preferably so proportioned that the circuit is tuned to resonance at the frequency of the alternating current supplied by the track transformer T with the result that the current will have a maximum value.

It is clear from the foregoing description that during one half cycle of the alternating current induced in the secondary winding I I of the transformer T2, the condenser CI takes sufficient charge to bring its plates to a potential difference substantially equal to the maximum value of the voltage induced in the secondary winding I I, and during the next half cycle of the alternating current, the condenser CI discharges in series with the secondary winding I I through the rectifying unit R2 to energize the winding of the track relay TR. Likewise, condenser C2 is charged during one half cycle of the alternating current induced in the secondary winding I I to bring its plates to a potential difference substantially equal to the maximum value of the voltage of the secondary Winding I I and then during the next half cycle of the alternating current, the condenser C2 discharges in series with the secondary winding II through the rectifying unit RI to energize the winding of the track relay TR. The arrangement is such that the condensers CI and C2 are charged during opposite half cycles of the alternating current and hence discharge alternately. Consequently, an electromotive force of substantially double that induced in the secondary winding I I is applied across the winding of the track relay TR, during the full wave of the alternating current, the rectifying units RI and R2 being so arranged that the current flows in the winding of the relay TR always in the same direction. The two receiving circuits over which the opposite half cycles of the alternating current are supplied to the relay TR being tuned to resonance at the frequency of the alternating current, the current will have a maximum value. It is to be noted that the current supplied to the relay TR. is proportional to the capacity of the condensers CI and C2. The condensers CI and C2 and the associated apparatus are so proportioned that the required working value of current necessary for relays of the type here involved is assured.

When a train enters the section A-B and shunts the trafiic rails, the voltage across the primary winding 8 of the transformer T2 will be greatly reduced and the voltage induced in the secondary winding II will be correspondingly reduced, and in turn, the unidirectional current supplied to the relay TR will be reduced to release the armature 28. Furthermore, the shunting of the primary winding 8 of the transformer T2 will be effective to vary the inductance of the secondary winding II, and, consequently, the circuit including the secondary winding I I, condenser CI and winding of the relay TR; and the circuit including the secondary winding II, condenser C2 and the winding of the relay TR will both be de-tuned, which will effect a still further reduction in the current flowing in the winding of the relay TR with the result that the release of the armature 2!] will be expedited.

It should be noted that dependence need not be placed alone on the change in inductance occasioned by the shunting of the primary winding 8 by the train, for the improvement in shunting sensitivity, as considerable improvement can be obtained without resorting to the tuned circuit. As is well known, the copper oxide rectifier (as well as certain other rectifiersof this type, such as the selenium rectifier) possesses the property of increasing its resistance to a marked extent with a relatively small decrease in potential across its terminals. Therefore, when a train enters the section, and reduces the voltage of winding I I, the rectifier resistance is considerably increased and if the parts are properly proportioned, this increased resistance will prevent condensers CI and C2 from reaching their peak charge correspendin to the ma m 'vo ta ec w n 1 during the half-wave period when the charging current is effective. Consequently, the voltage across relay -TR will be ,reduced in greater proportion than the voltage of winding 1 I, and in- .creased shunting sensitivity will therefore result.

I have found that by using properly matched apparatus the shunting time for the track relay TR will be materially reduced from that obtained by customary contemporary track circuit apparatus. Furthermore, I have found that with track circuit apparatus embodying my invention, the shunting sensitivity of the track circuit is materially increased over that obtained in present day practice.

In Fig. 2, the input terminals l2 and I3 of the voltage doubler network VD are connected directly withthe trafiic rails l and .la by wires 9 and H], respectively, the transformer T2 of Fig. 1 being omitted. The winding of the track relay TR is connected with the output terminals l6 and I! of the voltage doubler VD the same as in Fig. 1. During the half cycle of the alternating current that the trafiic rail I is positive the condenser C! takes a charge sufficient to bring the potential difference of its-plates substantially to the maximum value of the voltage across the trafiic rails, and then during the next half cycle, the condenser Cl discharges in series with the source of current 'for the track circuit through the winding of the relay TR with the result that the voltage applied across the relay TR is substantially double the voltage across the tralfic rails. During the half cycle that the traflicrail .la. is positive, the condenser CZ takes a charge suificient to bring the potential difference of its plates substantially to the maximum value of the voltage across the traflic rails, and thenon the next half cycle of the alternating current, the condenser C2 discharges in series with the source ofalternating current through the relay TR with the resultthat during this half cycle, a voltage substantially double that existing across the trafiic rails is applied to the track relay TR. It is clear that the apparatus of Fig. 2 will be effective to quickly release the armature of the track relay TB in response to a train enteringthe associated section in the same manner asdescribed for the apparatus of Fig. 1, dependence being placedon the voltage-resistance characteristic of the rectifier, or thechange in inductance of the track circuit when shunted by a train, or on both of these factors.

Track circuit apparatus such ashere disclosed will be effective to. give a veryquick release action of the track. relay in: response to a train entering the section, and the track relay will shunt with a relatively high resistance across the traflic rails.

Although I have herein shown and described only two forms of apparatusembodying my invention, it is understoodfthat various changes and modifications may be made therein within the scope of the appendedclaims without departing .from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with a sectionof railway track and a source oflperiodic. current connected across the trafiic rails of the .section, a. direct current relay, a circuit network comprising four arms two successive arms of which each include an asymmetric unit and two successive arms of which each include a. .condenser,; means for supincluding the other condenser, and a tratfic across the traflic rails of the section, adirect ru ns th er o c cur e pm h tra r s across the terminal common to the two arms including the asymetric units andthe terminal common to the two arms including the condensers,

means for connecting the winding of said relay across the terminal common to an arm including one asymmetric unit and the arm including one condenser and theterminal common to the arm including the other asymmetric unit and the governing armature controlled by said relay.

2. In combination with a section of railway track and a source of periodic current connected across-the trafiic rails of the section, a direct rent relay; a bridge circuit network comprisinga first arm including a first asymmetric unit, a second arm including a first condenser, a third arm'including a second condenser and a fourth arm including a second asymmetricunit; means forsupplying the periodic current fromthe-traiffijc' rails across the terminal common tothefirst and fourth armsvand the terminal common to the second and third arms, means for connecting the winding of said relayacross the terminal common to the first and second arms and the terminal common to the third and fourtharms, and a traific controlling armature governedby said relay.

3. In combination with a section of railway track and a source of periodic current connected current relay; a bridge circuit network comprising a first arm including a first asymmetric unit, a

.second arm including a first condenser, a third arm including a second condenser and a fourth arm including a second asymmetric unit; atransformer having its primary winding connected across the traffic rails, meansfor connecting-the secondary winding across the terminal common to the first and fourth arms andthe terminal common to the second and third arms, and means :for connectingthe winding of said relay ac1 o ss the terminal common to the first and second arms and the terminal common to-the third and fourth arms.

4. In combination with a section of railway track and a source of alternating current connected across the trafiic rails of the section, a

transformer having its primary winding connected across the traiiic rails of the section to 5p receivethe alternating current, a direct current relay, a condenser, a first and a second asy mmetric unit, means for connecting said condenser .andthe first asymmetric unit in series across-the secondary winding of said transformer; and

means-for connecting the condenser, winding of said relay and the second asymmetric unit in .nected across the trafficrails of the section, a

direct current relay, a transformer having its 7 primary winding connected across the trafiic rails of;the section, a condenser, a first and a secon d asymmetric unit, means for connecting said condenser and the first asymmetric unit in series to charge the condenser during one half cycle of the alternating current; and means for connecting the condenser, winding of the relay and the second asymmetric unit in series across the secondary winding of the transformer to supply current of double the voltage of said transformer to the winding of the relay during the other half cycle of the alternating current.

6. In combination with a section of railway track and a source of alternating current connected across the traffic rails of the section, a transformer having its primary winding connected across the tramc rails to receive the alternating current, a direct current relay; a first receiving circuit including the secondary winding of said transformer, a first condenser, the winding of said relay and a first asymmetric unit in series; said first circuit tuned to resonance at the frequency of the alternating current and arranged to pass one half cycle of the alternating current; and a second receiving circuit including the secondary winding of the transformer, a second condenser, the winding of said relay and a second asymmetric unit; said second circuit tuned to resonance at the frequency of the alternating current and arranged to pass the other half cycle of the alternating current, whereby shunting of the trafiic rails is effective to de-tune said circuits for expediting the release of the relay.

7. In combination with a section of railway track and a source of alternating current connected across the traflic rails of the section, a direct current relay, a condenser, circuit means for connecting said condenser across the traffic rails including a first asymmetric unit for charging the condenser during one half cycle of the alternating current, and a receiving circuit for .connecting the winding of said relay across the traffic rails including said condenser and a second asymmetric unit for energizing the relay during the other half cycle of the alternating current, said receiving circuit tuned to resonance at the frequency of the alternating current whereby shunting of the trafiic rails is effective to de-tune said circuit for expediting the release of said relay.

8. In combination with a section of railway track and a source of alternating current connected across the traffic rails of the section, a transformer having its primary Winding connected across the trafiic rails to receive the alternating current, a direct current relay, a condenser, means for connecting said condenser across the secondary winding of the transformer including a first asymmetric unit for charging said condenser during one half cycle of the alternating current, and a receiving circuit for connecting the winding of the relay across the secondary winding of the transformer including said condenser and a second asymmetric unit for energizing said relay during the other half cycle of the alternating current, said receiving circuit tuned to resonance at the frequency of the alternating current whereby shunting of the traific rails is efiective to de-tune said circuit for ex-, pediting the release of said relay.

9. In combination with a section of railway track and a source of periodic current connected across the traific rails of the section, a direct current relay; a bridge circuit network comprising a first arm including a first copper oxide rectifier, a second arm including a first condenser, a third arm including a second condenser and a fourth arm including a second copper oxide rectifier;

'means for supplying the periodic current from the traffic rails across the terminal common to the first and fourth arms and the terminal common to the second and third arms, means for connecting the winding of said relay across the terminal common to the first and. second arms and the terminal common to the third and fourth arms, and a traific controlling armature governed by said relay.

10. In combination with a section of railway track and a source of periodic current connected across the trafiic rails of the section, a direct current relay; a bridge circuit network comprising a first arm including a first copper oxide rectifier, a second arm including a first condenser, a third arm including a second condenser and a fourth arm including a second copper oxide rectifier; a transformer having its primary winding connected across the traffic rails, means for connecting the secondary winding across the terminal common to the first and fourth arms and the terminal common to the second and third arms, and means for connecting the winding of said relay across the terminal common to the first and second arms and the terminal common to the third and fourth arms.

11. In combination with a section of railway track and a source of alternating current connected across the trafiic rails of the section, a transformer having its primary winding connected across the tramc rails of the section to receive the alternating current, a directscurrent relay, a condenser, a first and a second copper oxide rectifier, means for connecting said condenser and the first copper oxide rectifier in series across the secondary winding of said transformer; and means for connecting the condenser, winding of said relay and the second copper oxide rectifier in series across the secondary winding of the transformer; said copper oxide rectifiers being arranged to pass currents of opposite polarities whereby the condenser takes a charge during onehalf cycle of the alternating current and then functions in series with the secondary winding of the transformer to supply current to the winding of the relay during the other half cycle of the direct current relay, a transformer having its primary winding connected across the traffic rails of the section, a condenser, a first and a second copper oxide rectifier, means for connecting said condenser and the first copper oxide rectifier in series across the secondary winding of the transformer to charge the condenser during one half cycle of the alternating current; and means for connecting the condenser, winding of the relay and the second copper oxide rectifier in series across the secondary winding of the transformer to supply current of increased voltage to the winding of the relay during the other half cycle of the alternating current.

13. In combination with a section of railway track and a source of periodic current connected across the traffic rails of the section, a direct current relay; a bridge circuit network comprising a first arm including a first rectifier characterized by increased resistance with a decrease in potential applied thereto, a second arm including a first condenser, a third arm including a second condenser and a fourth arm including a second rectifier characterized by increased resistance with a decrease in potential applied thereto; means for supplying the periodic current from the traflic rails across the terminal common to the first and fourth arms and the terminal common to the second and third arms, means for connecting the winding of said relay across the terminal common to the first and second arms and the terminal common to the third and fourth arms, and a trafiic controlling armature governed by said relay.

14. In combination with a section of railway track and a source of alternating current connected across the traffic rails of the section, a direct current relay, a transformer having its primary winding connected across the traffic rails of the section, a condenser, a first and a second rectifier each characterized by increased resistance with a decrease in potential applied thereto, means for connecting said condenser and the first rectifier in series across the secondary Winding of the transformer to charge the condenser during one half cycle of the alternating current; and means for connecting the condenser, winding of the relay and the second rectifier in series across the secondary winding of the transformer to supply current of increased voltage to the winding of the relay during the other half cycle of the alternating current.

HAROLD G. WITMER. 

